Dielectric screening in perovskite photovoltaics

Abstract

The performance of perovskite photovoltaics is fundamentally impeded by the presence of undesirable defects that contribute to non-radiative losses within the devices. Although mitigating these losses has been extensively reported by numerous passivation strategies, a detailed understanding of loss origins within the devices remains elusive. Here, we demonstrate that the defect capturing probability estimated by the capture cross-section is decreased by varying the dielectric response, producing the dielectric screening effect in the perovskite. The resulting perovskites also show reduced surface recombination and a weaker electron-phonon coupling. All of these boost the power conversion efficiency to 22.3% for an inverted perovskite photovoltaic device with a high open-circuit voltage of 1.25 V and a low voltage deficit of 0.37 V (a bandgap ~1.62 eV). Our results provide not only an in-depth understanding of the carrier capture processes in perovskites, but also a promising pathway for realizing highly efficient devices via dielectric regulation.

Perovskite Solar Cells Go Bifacial—Mutual Benefits for Efficiency and Durability

“…[52][53][54] The ionic nature of the perovskite crystal also provides a dielectric screening effect to suppress the Coulomb interactions between carriers and ionic defects in the lattice. [55] The low intrinsic scattering rates in the bulk perovskite, along with the extrinsic control of grain boundaries and imperfections via engineering the deposition processes, contribute to the decent charge carrier mobility values of a few to tens of cm 2 V −1 s −1 . [56] The combination of high mobility values, long carrier lifetimes, and small effective masses results in long carrier-diffusion lengths of several micrometers, [57] which enable the thin-film device architectures to present high-efficiency PSCs.…”

An Integrated Bulk and Surface Modification Strategy for Gas‐Quenched Inverted Perovskite Solar Cells with Efficiencies Exceeding 22%

“…The EQE EL of the control PSC is 0.041%, whereas it is 0.92% for the BASCN‐treated PSC, which is 20 times higher. Based on the following Equation () [ 53 ] The V oc loss is reduced from 201 to 121 mV after the BASCN treatment, indicating effective passivation of the nonradiative recombination centers. In addition, hole‐only devices were prepared to evaluate the trap density of the control and BASCN‐treated perovskite films based on the pulsed space–charge‐limited current measurements (Figure S12, Supporting Information).…”

“…The EQE EL of the control PSC is 0.041%, whereas it is 0.92% for the BASCN-treated PSC, which is 20 times higher. Based on the following Equation (2) [53] V oc loss ¼ kT q ln 1 EQE EL…”

On the Investigation of Interface Defects of Solar Cells: Lead-Based vs Lead-Free Perovskite

“…In [61], it was shown the liquid-like molecular reorientation motions in the perovskite allow the effective carrier screening. In addition, in [62], the potassium halide species at the grain boundaries was observed to lower the capture cross section.…”