Removing Leakage and Surface Recombination in Planar Perovskite Solar Cells

Thin-film solar cells suffer from various types of recombination, of which leakage current usually dominates at lower voltages. Herein, we demonstrate first a three-order reduction of the shunt loss mechanism in planar methylammonium lead iodide perovskite solar cells by replacing the commonly used hole transport layer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with a better hole-selective polyarylamine. As a result, these cells exhibit superior operation under reduced light conditions, which we demonstrate for the extreme case of moonlight irradiance, at which open-circuit voltages of 530 mV can still be obtained. By the shunt removal we also observe the VOC to dro…

Unravelling steady-state bulk recombination dynamics in thick efficient vacuum-deposited perovskite solar cells by transient methods

Accurately identifying and understanding the dominant charge carrier recombination mechanism in perovskite solar cells are of crucial importance for further improvements of this already promising photovoltaic technology. Both optical and electrical transient methods have previously been employed to strive for this warranted goal. However, electrical techniques can be strongly influenced by the capacitive response of the device which hides the carrier recombination dynamics that are relevant under steady state conditions. To ascertain the identification of steady state relevant charge carrier dynamics, it is beneficial to evaluate thicker films to minimize the impact of device capacitance. H…

Reduced Recombination Losses in Evaporated Perovskite Solar Cells by Postfabrication Treatment

The photovoltaic perovskite research community has now developed a large set of tools and techniques to improve the power conversion efficiency (PCE). One such arcane trick is to allow the finished devices to dwell in time, and the PCE often improves. Herein, a mild postannealing procedure is implemented on coevaporated perovskite solar cells confirming a substantial PCE improvement, mainly attributed to an increased open-circuit voltage (V\(_{OC}\)). From a V\(_{OC}\) of around 1.11 V directly after preparation, the voltage improves to more than 1.18 V by temporal and thermal annealing. To clarify the origin of this annealing effect, an in-depth device experimental and simulation character…

Transient drift‐diffusion simulation of the open circuit voltage decay in ionic perovskite solar cells

Effects of Masking on Open-Circuit Voltage and Fill Factor in Solar Cells

Guidelines for the correct measurement protocol of novel photovoltaic technologies such as perovskites are becoming more frequent in literature. This because, as will be confirmed in this perspective, it is not straightforward to correctly measure the efficiency parameters of these and many other novel solar cells. This is particularly the case for small area research devices which are prone to overestimate the short circuit current density, due to edge effects of various types. To reduce the inaccuracy of current density determination, the common recommended practice is to utilize masks with well‐defined apertures, often smaller than the device active area. Herein we show both experimental…

Assigning ionic properties in perovskite solar cells; a unifying transient simulation/experimental study

Kinetic modelling has proven to be essential to understand the time and spatial dependence of charge carriers in solar cells. Traditional drift–diffusion simulations have generally been employed to describe static steady-state conditions, whereas recently the transient counterpart has been able to reveal more detailed information regarding carrier kinetics. In addition to customary electron and hole dynamics, perovskite materials are known to also be strongly affected by the displacement of lattice vacancies, charged atoms or even entire molecules. Such ionic motion transpires on vastly different time scales compared to free charges and are generally not straightforward to simultaneously ac…

Efficient Monolithic Perovskite/Perovskite Tandem Solar Cells

Thin-film solar cells suffer from various types of recombination, of which leakage current usually dominates at lower voltages. Herein, we demonstrate first a three-order reduction of the shunt loss mechanism in planar methylammonium lead iodide perovskite solar cells by replacing the commonly used hole transport layer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with a better hole-selective polyarylamine. As a result, these cells exhibit superior operation under reduced light conditions, which we demonstrate for the extreme case of moonlight irradiance, at which open-circuit voltages of 530 mV can still be obtained. By the shunt removal we also observe the VOC to dro…