Highly transparent conductive, aluminum-doped zinc oxide (ZnO:Al) films were deposited on glass substrates by midfrequency magnetron sputtering of metallic aluminum-doped zinc target. ZnO:Al films with surface work functions between 3.7 and 4.4 eV were obtained by varying the sputtering conditions. Organic light-emitting diodes (OLEDs) were fabricated on these ZnO:Al films. A current efficiency of higher than 3.7 cd/A, was achieved. For comparison, 3.9 cd/A was achieved by the reference OLEDs fabricated on commercial indium–tin–oxide substrates.

Rational hole transport layer (HTL) material design is regarded as one of the most important approaches to improve the efficiency and stability of perovskite solar cells (PSCs). Herein, we investigate the effect of a widely spread p-type dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) on the optical and electrical properties of conventional poly(3,4-ethylenedioxythiophene):poly-(styrene sulfonate) (PEDOT:PSS) HTLs, as well as the photovoltaic performance of the corresponding perovskite solar cells. Doping F4-TCNQ at a low concentration can efficiently adjust the electrical properties of the PEDOT:PSS film and lower the highest occupied molecular orbital (HOMO) level. As a result, the enhanced electrical conductivity and energetically favorable energy level alignment of the doped film allow efficient carrier transport from the perovskite absorber layer to the HTL. Finally, the PSCs with the F4-TCNQ doped HTL exhibited simultaneously increased short-circuit current (J_sc), open circuit voltage (V_oc) and fill factor (FF). The highest power conversion efficiency (PCE) was notably improved from 13.30% (undoped) to 17.22% (0.30 wt% of F4-TCNQ doping), suggesting that the F4-TCNQ doped PEDOT:PSS film is an efficient HTL to achieve high performance perovskite solar cells.