Poly(3,4ethylenedioxythiophene): Poly(styrenesulfonate)/GaAs hybrid solar cells with 13% power conversion efficiency using front-and back-surface field

Planar hybrid solar cells based on bulk GaAs wafers with a background doping density of 10¹⁶ cm^-3 and poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) demonstrated an excellent power conversion efficiency of 8.99%. The efficiency of the cell was enhanced to 9.87% with a back-surface field feature using a molecular beam epitaxially grown n-type GaAs epi-layer. The efficiency and fill factor reach 11.86% and 0.8 when an additional p + GaAs epi-layer is deposited on the surface of the solar cells, which provides a front-surface field. The interface between the high-and low-doped regions in the polymer/GaAs and GaAs formed an electric field that introduced a barrier to minority carriers flow to the substrate and effectively reduced front surface carrier recombination, thereby enhancing light-generated free carrier collection efficiency and open-circuit voltage. Compared with the device without the front-and back-surface field, the fill factor and open-circuit voltage of the hybrid solar cell were improved from 0.76 to 0.8 and from 0.68 V to 0.77V, respectively. The highest efficiency reaches a record 13% when the Zonyl fluorosurfactant-treated PEDOT:PSS is used as a holetransporting conducting layer for hybrid cells.