光處理技術應用於混合型有機/砷化鎵太陽電池

Abstract

近幾年興起以有機材料搭配無機半導體之混合式太陽電池備受矚目。目前由P-type的PEDOT:PSS加上N-type砷化鎵混合型太陽電池效率可達7%。本論文主要研究分為三部分:其一，利用表面結構增加吸光機率，在濕蝕刻技術上利用硝酸配硫酸和氨水配雙氧水進行蝕刻，成功將反射率降至13%並使元件的光電流從17.49 mA/cm2提升23.31 mA/cm2，平均光電轉換效率從7.8%提升9.4%。在乾蝕刻技術上，反射率降至8.86%並使元件的平均光電流從16.17 mA/cm2提升19.60 mA/cm2，平均光電轉換效率從7.11%提升7.42%。 其二在有結構的砷化鎵元件旋上有機層TAPC / Green B，其有機層可視為中間複合層，降低表面複合的機會且提升Voc。元件最佳結果開路電壓0.645V、短路電流25.15 mA/cm2、填充因子61.78%、光電轉換效率達到10%。 最後砷化鎵基板具有極好的光吸收性，僅需幾個微米的厚度就能吸大部分的光並根據光子回收模型，開路電壓能有進一步提升。第三部分進行混合型太陽電池基板移除並加上背反射鏡並在模擬的輔助下。實驗結果顯示開路電壓從0.66V提升到0.7V，定性上與模擬結果相符合

In recent years, the emergence of hybrid organic and inorganic semiconductor solar cells attracts a lot of attention. Currently, GaAs hybrid solar cells which combine p-type PEDOT:PSS with n-type Gallium Arsenide(GaAs) can achieve a power conversion efficiency (PCE) of 7%. This thesis is divided into three parts. In the first part, we employ surface structures to increase the light absorption. By using a wet etching technique, we mix nitric acid with sulfuric acid and ammonia water mixed with hydrogen peroxide to etch GaAs surface. The reflectance was reduced to 13%, leading to a short-circuit current increase (Jsc) from 17.49 mA/cm2 to 23.3 mA/cm2 and an average PCE from 7.8% to 9.4%.By using a dry etching technique, the reflectance was reduced to 8.86%, leading to a Jsc increase from 16.17 mA/cm2 to 19.6 mA/cm2, and an average PCE from 7.11% to 7.42%. In the first part, we introduce organic materials TAPC and Green B into the GaAs interface. The intermediate layer functions as a recombination layer, which can reduce the chance of surface recombination and enhance the open-circuit voltage (Voc). The best device shows that the PCE can achieve 10% with Voc, Jsc and fill-factor equal to 0.645V, 25.15 mA/cm2, and 61.78%, respectively. Finally, GaAs has high absorption coefficients and a thickness of several micrometers is enough for light absorption. According to the detailed balance theory, we can further enhance the Voc by placing a good mirror on the back of a cell. In the third part, we use the wafer lift-off process to remove the substrate of GaAs hybrid solar cell and then metal bond to a silicon substrate with a gold back reflector. Our experiment result shows that the wafer-bonding cell has an average Voc of 0.7V with a net increase of 0.04V, which is qualitatively consistent with the simulation result.