能源科技與環境概論 太陽能電池導論 Hsing-Yu Tuan ( 段興宇 ) Department of Chemical Engineering, National Tsing- Hua University
Various types of solar cells silicon single crystalline crystalline polycrystalline thin film amorphous solar cells compound single crystalline poly crystalline thin film III-V(GaAs) CIGS CdTe organic dye sensitized polymer
Pick right materials as absorption layer - Good absorption coefficient to harvest light - Suitable band gap
Direct band gap and indirect band gap structure -We prefer direct semiconductor materials since they can absorb light more efficiently E E E Direct Bandgap E g CB E c E v Photon CB Indirect Bandgap, E g k cb E c E r CB E c Phonon k VB k k VB k vb E v k k VB E v k (a) GaAs (b) Si (c) Si with a recombination center (a) In GaAs the minimum of the CB is directly above the maximum of the VB. GaAs is therefore a direct bandgap semiconductor. (b) In Si, the minimum of the CB is displaced from the maximum of the VB and Si is an indirect bandgap semiconductor. (c) Recombination of an electron and a hole in Si involves a recombination center.?1999 S.O. Kasap, Optoelectronics (Prentice Hall)
Absorption of semiconductors -Si and Ge s absorption coefficient increase slowly with increased energy
ηmax(%) vs Eg (ev) under AM1.5 real η max is only around 30% due to loss of other facters Eg: 1.0 1.5 ev is the best range
Semiconductor band, using Si as an example Covalent bond Si ion core (+4e) Electron energy, E E c +χ Conduction Band (CB) Empty of electrons at 0 K. E c Band gap = E g E v (a) 0 (b) Valence Band (VB) Full of electrons at 0 K. (a) A simplified two dimensional view of a region of the Si crystal showing covalent bonds. (b) The energy band diagram of electrons in the Si crystal at absolute zero of temperature.?1999 S.O. Kasap, Optoelectronics (Prentice Hall)
Doping of Si: increase the conductivity of intrinsic Si Donors: P, As, Sb (Column V elements ), n-type, provide one additional electron Acceptors: B, Ga, In, (Column III elements), p-type provide one additional hole Donors EB Acceptors EB P+ - B- Sb 0.039 ev B 0.045 ev P 0.044 ev Al 0.057 ev As 0.049 ev Ga 0.065 ev In 0.16 ev -weakly bound -bonding strength E B ~ 0.05 ev (Si bonding ~1.12 ev) Ec 0.044 ev (P) ED Majority carrier - electron in a n-type material hole in a p-type material Minority carrier hole in a n-type material electron in a p-type material EA Ev 0.057 ev (Al)
P-N junction
A PN junction photovoltaic device PN junction provide a Depletion region in where an electric field is created for drifting electron and hole -incoming photon generate EHPs and create current -generated electrons and hole can diffuse and drift in neural region and SCL, respectively -Opencircuit voltage (Voc) develops between the terminals of the device because the electrion reaches the neutral n and p, respectively.
Device structure of a Si solar cell (1) Finger electrodes Bus electrode (2) for current collection 0.2 μm n (3) surface texturization Incident light 200 μm p In order to capture more light - finger electrodes were made to allow light pass through the device - a thin antireflection coating on the surface reduces light reflection and allow more lighte to enter the device -surface texturization to for multiple light reflection and increase light path
Schematic of a semocnoductor solar cell
Video
IV curve of a solar cell η = Maximum PV output V = V = mp oc Incident solar J P in J P in mp sc 100% V V mp oc J J mp sc 100% power power( P in ) ( Pmp) 100% = V Voc (open circuit voltage) -when output current approaches zero, the voltage develops between two terminals ideally Voc~Eg at 0K and inverse proportional to temperature Jsc (short-circuit current) -like the device connect the device with metal circuit, close to photogenerated current FF (fill factor): We want FF close to 1 P oc mp J sc FF = J V ; FF mp / P in mp 100% = J J mp sc V V mp oc
J(mA/cm 2 ) 10 Solar cell efficiency :an example η and FF in this device? 9 8 7 6 5 4 Jsc J MP (0.55,5.9716) η=p MP /P in x100%=ff*v oc J sc / P in x100% ( 輸出電功率 / 入射光功率 ) P in =100 mw/cm 2 P MP =V MP *J MP =0.55*5.9716=3.28mW/cm 2 η =3.28/100*100%=3.28% 3 2 1 0 V MP Voc 0 0.2 0.4 0.6 0.8 1 V(V) V oc =0.72 V J sc =7.1464 ma/cm 2 FF=V MP *J MP /V oc *J sc =3.28/(0.72*7.14)=0.63 Voc: 開路電壓 (open circuit voltage), 當輸出電流趨近於零, 相對太陽電池兩電極端點沒有連接所得到的電壓 Jsc: 短路電流 (short circuit current) 如將照光的 pn 二極體兩端的金屬電極用金屬線連接, 造成短路, 此短路電流等於光電流
Various losses of solar energy of a Si solar cell during processing 100% Incident radiation 0.74 Insufficient photon energy hυ < E g Silicon band gap is 1.1 ev, and the device loses all photon energy less than 1.1 ev Only 43.6% remaining! 0.59 Excessive photon energy Near surface EHP recombination hυ > E g Excessive photon energy Near surface EHP recombination 0.95 Collection efficiency of photons 0.6 V oc (0.6E g )/(ek B ) 0.85 FF 0.85 Overall efficiency Antireflection coating is not perfect Voc is inverse proportional to temperature, so not equals to Eg device fabrication resistance η 21% Accounting for various losses of energy in a high efficiency Si solar cell. Adapted from C. Hu and R. M. White, Solar Cells (McGraw-Hill Inc, New York, 1983, Figure 3.17, p. 61).?1999 S.O. Kasap, Optoelectronics (Prentice Hall) The highest efficient of a real photovoltaic device that uses a single crystal of Si Is about 24.7% ( 澳洲新南威爾斯大學 )
Single/poly crystalline Si solar cell fabrication process P-type ingot was cut (the wafer are placed in a belt furnace And heated about 900 C etch in a strong acidic or alkaline solution The reflectivity is still round 30%,H:SiNx is deposited on the cell to reduce more the reflectivity etch in a weak acidic or alkaline solution metal contacts are made by screen printing liquid glass containing P is distributed on one side of the wafer by spraying or spinningand heated Metallic contacts are heated and Etch trough the antiflecton coating
Solar cells installation DC power
Next step of crystalline Si solar cell
Industry Poly- Silicon Solar Grade Silicon 福聚太陽能友達晶材寶德能源實聯能源科冠山陽科技 6 Companies 歷年廠家數 : 2005=40 2006=50 2007=76 2008=100 2009=123 2010>160 Company 貳 發展現況 ( 續 ) 五 我國太陽光電產業鏈 Up Stream Mid Stream Down Stream Ingots/ Wafer Si Ingot & Wafers 中美晶 綠能 合晶 統懋 峰毅 茂迪 旭晶能源 晶耀 達能 國碩 昱成光能 友達晶材 12 Companies Solar Cell Wafer-based Solar Cell -Mono-Si, Multi-Si, GaAs Thin-film Solar Cell -a-si/µ-si, CIS, -Dye Sensitized Solar Cell CPV Solar Cell 矽晶電池 : 茂迪 益通 旺能 昱晶 新日光 昇陽 茂矽 太陽光電 太極 燿華 長生能源 旭泓 亞崙 尚陽 強茂 樂福 聯景 元晶 英穩達 友達 矽薄膜電池 : 綠能 聯相 富陽 宇通 八陽 旭能 CIGS 電池 : 綠陽 新能 太陽海 正峰新 亞化 威奈聯合 台積電 聚光型電池 : 全新 華上 禧通 台達電 晶電 宏捷 華旭 億芳 瀚昱 海德威 太聚 綠源 吉泰 亞飛 禾晶 DSSC: 健鼎 福盈 永光 镸興 台塑 > 54Companies PV Modules 頂晶 知光 英懋達 生耀 科風 茂暘 錸德 有晴 大晶 全能 安集 茂鑫 強茂 有成 友達 綠晁 鼎笙 17Companies PV Module PV System & Installa tion Installation System Parts -Inverter, BOS Equipment Product Installation: 茂迪 台達電 廣運 友達 聯相 宇通 富陽 永盛能源 有成 綠能 大金 東城 冠宇宙 太陽動力 鼎鼎 聚恒 金華成 中國大陸電器 羅森 全面性 伸浦 崇越 統昱 永旭 台邦 傳典 高鋒 華旭環能 工易 耀能 上揚 錸德 光寶綠能 詠通 華城 亞力 駿成 曜晟 寶球 明宜 元太 伸浦 新世紀 金頓 海灣 泰新 安慶 昇暉 雄雞 System Parts: 台玻 元璋 太美 城東 力鋼 元一 高鋒 法隆 泉鋼 盈正豫順 明碁材料 達方 台虹 碩禾 致嘉 台塑 暘益 台聚 新輝 昇貿 宏致 泰和 建和興 科宥 Equipment: 均豪 廣運 欽揚 東遠 志聖 帆宣 北儒 翔勝 致茂 綠色 Product: 亞通 東城 強而青 鯨威 日光能 茂迪 中國大陸電器 同昱 旭辰 旭邦 科宥 信合 千附 永炬 日曜 宇能 智柏 登陽 誼成 森富國際 >100 Companies
歐洲與日本之電池產量由 2006 年市占率約 30% 下降至 2011 年的 10% 以下 太陽光電生產基地持續向亞洲移動趨勢不變, 中國大陸與臺灣生產比例近全球 70% 大陸挾其成本優勢與政策支持, 成為全球最大製造國,2011 年產值達 2536 億元人民幣 56.6% 11.4% 8.7% 6.0%3.1% 14.2% 2011 中國大陸 2010 46.4% 14.1% 13.2% 7.8% 4.7% 13.8% 台灣 2009 2008 2007 2006 37.5% 12.3% 19.8% 12.6% 4.4% 13.4% 32.7% 11.6% 25.1% 16.0% 5.5% 9.1% 28.1% 10.8% 27.4% 21.8% 6.4% 5.5% 15.1% 6.7% 28.2% 36.4% 6.9% 6.7% 歐洲日本美國其他 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Thin film solar cell: use Si as an example - required thickness of thin film solar cell is around 0.5 μm, 1/500 of that of wafer based solar cell - material cost is very low
Advantages of thin film solar cells 1. low raw materials are required for fabrication 2. light transmission is better 3. more competitive price (CdTe, US$1 per watt ; First Solar, stock price is US$180 ) 4. frameless design 5. Ideal for BIPV( building integrated photovoltaic)
Device structure of amorphous Si solar cell -a-si s absorption coefficient at visible light is one order of magnitude than c-si, so only 10-30 nm is needed to capture most photon in the visible region -thickness of p and n type are around 10-30nm, thickness of i layer is less than 500 nm
Structure of an amorphous Si solar cell
II-VI compound solar cell: CdTe Abbreviated periodic table I II III IV V VI B C N O Al Si P S Cu Zn Ga Ge As Se Ag Cd In Sn Sb Te II-VI group as light harvesting materials band gap of CdTe : 1.5 ev
Device structure of a CdTe solar cell P-type: CdTe n-type: CdS
First solar Pallas 綜合外電報導 / SolarExchange 美國太陽能廠商 First Solar 於去年第四季生產成本降到每瓦 0.98 美元美國太陽能模組製造商 First Solar(Nasdaq: FSLR) 於 24 日宣布, 2008 年第四季平均生產成本降到每瓦 0.98 美元, 成為首家低於每瓦 1 美元的太陽能廠商 美國太陽能模組製造商 First Solar(Nasdaq: FSLR) 於 24 日宣布,2008 年第四季平均生產成本降到每瓦 0.98 美元, 成為首家低於每瓦 1 美元的太陽能廠商 First Solar 於 2004 年開始商業化生產以來,2008 年產能成長約 2500 % 達到 500 MW 2009 年產能將再增加一倍, 達到 1GW 這相當於一般核電廠的規模 這些成長率隨著成本迅速降低而提高 生產成本自 2004 年以來降了超過三分之二, 從每瓦 3 美元降到每瓦 1 美元不到 First Solar 有信心能基於 First Solar 未用盡的技術和製程的潛力, 進一步再將成本降至更低 Current production Cost of crystalline Solar cell is around US 2/Wp
Band gap and optical absorption of CIGS CISe2:1.0 ev CIGS:1.0-1.6 ev CIS:1.3-1.5 ev Muller, semiconductor for solar cells, 1993 Efficiency = FFVocIsc Pin -CIGS s band gap is in the range of 1.1 to 1.5 ev
I-III-V2 compound solar cell: (CIGS) Schematic picture Current collection grid HR-ZnO/n+-ZnO (0.5µm) n-typecds (0.05 µm) Cu(InGa)Se2 (2µm) Mo (0.5 µm) Soda lime glass total device thickness less than 5 µm (Crystalline Si module~200 µm)
Compared to CdTe solar cells Schematic picture Current collection grid HR-ZnO/n+-ZnO (0.5µm) n-typecds (0.05 µm) Cu(InGa)Se2 (2µm) Mo (0.5 µm) Soda lime glass Much less Cd required
An example of vaccum-based CIGS film deposition Y. Hamakawa Thin-film solar cells,
Vaccum-based CIGS film deposition -Highest efficiency (lab scale: 18~20%) -Usually UHV/MBE -Cost prohibitive (but <cryst-si) General drawbacks: -Difficult to achieve controlled-stoichiometry over large device areas -Manufacturing equipment is very expensive (> NT 0.1 billion) -The deposition process is time-consuming -Poor materials utilization (30-50%) -Low throughput
Non-Vacuum Processing -Synthesize colloidal nanocrystals with controlled CIGS stoichiometry and deposit layer -Roll-to-roll manufractruing process 36
Nano solar- Nanoparticle as ink for printable solar cell CIGS particle ink Flexible solar cell Roll-to-roll processing Add a video has denmostrated a 1GW coater in a movie 37
Process Silicon Wafer cells Si wafer processing Vacuumbased thin film High vacuum depositon Roll-printed thin film Roll-to-roll printing Process Robust Fragile Robust Yield Materials Utilization 30% 30-60% Over 97% Throughput 1 2-5 10-25
Nanosolar, Thin-Film Solar Hype Firm, Officially Dead U.S. CIGS solar assets are being auctioned off after more than $400 million in VC investment. by Eric Wesoff July 12, 2013
CIGS Rocks! 2010/July 時報記者沈培華台北報導 台積電 (2330) 新事業總經理蔡力行表示, 台積電將以 CIGS 薄膜產品進軍太陽能產業, 以五年期間朝全球前五大廠邁進, 產能規模將達 1GW 規模, 並看好此事業對台積電是有獲利與高成長潛力的新事業 台積電今天舉行先進薄膜太陽能技術研發中心暨先期量產廠房動土典禮 新事業總經理蔡力行表示, 全球太陽能電池市場將持續成長, 預期 2009 年至 2015 年全球太陽能電池市場年複合成長率可望達 23%; 其中, 銅銦鎵硒 (CIGS) 因具有薄膜的低成本價格等優勢, 成長率將最高, 年複合成長率將達 115% 台積電因此將以 CIGS 薄膜產品為主力, 進軍太陽能產業 台積電先進薄膜太陽能廠第一期將投資約 79.2 億, 預計 2012 年量產 200 百萬瓦 (MW), 終期產能為 700 百萬瓦 (MW) 台積電董事長張忠謀並預估,2015 年太陽能佔台積電營收比重可望達 10% 蔡力行表示, 台積電三年內 CIGS 薄膜太陽能電池模組轉換效率將達 14%, 產能規模將約 300 至 500 百萬瓦, 預期 3 至 5 年轉換效率將進一步提升至 16%, 產能規模將達 1GW 規模
薄膜太陽能翻身台積電產能衝 3 倍全球龍頭廠轉盈產業前景漸撥雲見日 2014/Feb 台積電旗下銅銦鎵硒 (CIGS) 薄膜太陽能廠目前年產能為 40 百萬瓦 (MWp), 隨著整體市況轉佳 訂單滿載且技術獲得重大突破, 台積電第 4 季 CIGS 年產能將擴增到 120MWp, 達到 3 倍規模, 太陽能業者透露, 以台積電在太陽能領域穩紮穩打風格來看, 這次產能出現大躍進, 凸顯 CIGS 接單情況明顯轉佳, 業界紛預期台積電太陽能事業可望邁向獲利 不過, 台積電發言體系表示, 目前針對財務部分不予置評 全球最具代表性的 CIGS 薄膜太陽能龍頭大廠是日本昭和殼牌石油旗下子公司 Solar Frontier, 年產能規模達 900MWp, 近年來一直陷入虧損困境翻不了身, 然近期財報終於首度轉虧為盈,2013 年旗下產能全數滿載, 年營收暴增 8 成, 並計劃在日本東北 (Tohoku) 擴增 150MWp 產能的 CIGS 新廠, 預計 2015 年投產
台積太陽能步上關廠業界 : 成本難敵 矽晶 2015/08/25 16:36 ( 中央社記者張建中新竹 25 日電 ) 台積電 100% 持股子公司台積太陽能將於 8 月底結束工廠營運 業界人士認為, 薄膜太陽能電池成本難敵矽晶太陽能電池, 是迫使台積太陽能走向關廠的主因 台積電新事業發展接連遭逢重大挫敗, 旗下台積固態照明因較晚進入發光二極體 (LED) 產業, 業界專利障礙與通路開發不易, 考量短期難以轉盈, 台積電今年初決定將台積固態照明全部股份賣予晶電 台積電今天又宣布, 旗下台積太陽能因是市場後進者, 缺乏經濟規模, 雖然轉換效率具領先優勢, 但在成本上不具競爭力, 即便執行最精進的成本減抑計畫, 也將難以逆轉成本劣勢, 將於 8 月底結束工廠營運 台積電是於 2009 年成立新事業部, 並陸續成立台積固態照明與台積太陽能, 分別投入 LED 與太陽能產業, 由前總執行長蔡力行領軍 隨著蔡力行轉往中華電信擔任董事長, 台積固態照明與台積太陽能董事長由左大川接任 台積太陽能成立之初, 蔡力行曾表示, 台積太陽能將以技術領先為主要策略
Comparison of three thin film solar cells Semiconductor Taiwan 2008
Tandom Junction Solar cells
Market distribution in 2009