Improved UV sensitivity and charge transport in PTB7-Th:PC71BM solar cells doped with cadmium selenide quantum dots

Abstract

Three chromium selenide quantum dots (CdSe QDs) with different emissions have been incorporated into PTB7-Th:PC₇₁BM BHJ active layers to fabricate polymer solar cells (PSCs). It has been proved that CdSe QDs gather on the top surface of active layers. The photon harvesting efficiency in the ultraviolet region improved and the charge transport capacity enhanced in all CdSe QD-doped PSCs due to the high photoluminescence quantum yield (PLQY) of the ultraviolet light conversion to visible light and the high conductivity of CdSe QDs, respectively, which leads to a higher short circuit current (J_sc) and fill factor (FF). However, CdSe QDs with different PL emissions have different effects on the performance of PSCs. CdSe QDs with 623 nm emission is more effective in promoting photon harvesting in the ultraviolet region but gives a smaller effect to improve the charge transport than that emitted by CdSe QDs at 525 nm and 462 nm. It results in almost the same efficiency of the three devices doped with different CdSe QDs at different PL emissions. Finally, the power conversion efficiency (PCE) improved from 8.87% of the control device to 9.77%, 9.71%, and 9.75% of the three devices with CdSe QDs, respectively.