Abstract
It is well known that [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is a common n-type passivation material in PSCs, usually used as an interface modification layer. However, PCBM is extremely expensive and is not suitable for future industrialization. Herein, the various concentrations of PCBM as an additive are adopted for PSCs. It not only avoids the routine process of spin coating the multi-layer films, but also reduces the PCBM material and cost. Meanwhile, PCBM can passivate the grain surface and modulate morphology of perovskite films. Furthermore, the most important optical parameters of solar cells, the current density (Jsc), fill factor (FF), open-circuit voltage (Voc) and power conversion efficiencies (PCE) were improved. Especially, when the PCBM doping ratio in CH3NH3PbI3 (MAPbI3) precursor solution was 1 wt%, the device obtained the smallest Voc decay (less than 1%) in the p-i-n type PSCs with poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) as hole transport layer (HTL) and fullerene (C60) as electron transport layer (ETL). The PSCs Voc stability improvement is attributed to enhanced crystallinity of photoactive layer and decreased non-radiative recombination by PCBM doping in the perovskites.
Highlights
When the phenyl-C61-butyric acid methyl ester (PCBM) doping concentration in MAPbI3 precursor solution was from 0 - 1 wt%, the Jsc, fill factor (FF) and Voc of the devices increased, the Voc of the planar ITO/PEDOT:PSS/MAPbI3 with PCBM/C60/BCP/Ag (p-i-n) device structure reached more than 0.99 V, and the Voc loss was less than 1% compared with the theoretical value
It can be seen from the pristine and PCBM-perovskite thin films PL spectrum shown in Figure 1(b) that the PL emission peak centered at 766 nm did not change even when the dose of PCBM in perovskite films increased, and the obtained band gap of perovskite was about 1.61 eV
PCBM concentrations (W/O, 0.5 wt%, 1.0 wt% and 1.5 wt%) were 982 ns, 1057 ns, 1056 ns, and 904 ns, respectively. These results indicated a faster photogenerated carrier extraction for ITO/PEDOT:PSS/perovskite films with slight PCBM, which was beneficial to the Jsc and power conversion efficiencies (PCE) values of the devices
Summary
Organic-inorganic hybrid PSCs have recently drawn tremendous attention because of their simple solution processing, tunable optoelectronic properties, high carrier migration, low photo exciton binding energy, excellent bi-polar carrier. Many studies have proved that in high-efficiency PSCs, C60 and its derivative PCBM have excellent electron acceptability due to the spherical structural strain, making this kind of material the most effective passivation agent. The PSCs have higher carrier mobility and longer carrier life-times, the whole device will still have non-radiative recombination, which limits their Voc value below the Shockley-Queisser theory [30] [31] In this experiment, it was found that doped PCBM could passivate perovskite, increase grain size, and improve the cells’ Voc. When the PCBM doping concentration in MAPbI3 precursor solution was from 0 - 1 wt%, the Jsc, FF and Voc of the devices increased, the Voc of the planar ITO/PEDOT:PSS/MAPbI3 with PCBM/C60/BCP/Ag (p-i-n) device structure reached more than 0.99 V, and the Voc loss was less than 1% compared with the theoretical value
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