A new algorithm for the maximum power point tracking (MPPT) method has been developed in order to determine the maximum power (P max) for slow-responding metastable PV devices such as perovskite solar cells (PSCs). It is well known that such devices often cause significant P max oscillation during a standard MPPT measurement. This oscillation was found to occur caused by difference in the current acquired after increasing the voltage and that acquired after decreasing the voltage. The new algorithm developed in this paper has eliminated such oscillation with comparison between the powers at different voltages after changing the voltage in the same direction. P max data determined by using this algorithm were found to be reliable by comparing with those determined by the dynamic I-V measurements.

Perovskite solar cells (PSCs) are expected to be one of the next generation photovoltaics. However, reliable measurements of the power conversion efficiency (PCE) of PSCs are challenging as changes in the electrical properties occur during the conventional I-V curve measurements. In order to solve this problem, several methods to maximize the accuracy have been developed, but consistency between these methods has not been verified. In this paper, a round-robin inter-comparison of the maximum power measurements for metastable perovskite solar cells has been performed among three public laboratories in Japan using several methods. The maximum powers determined by the three laboratories using the conventional I-V curve measurement technique defined in IEC 60904-1 were compared to each other. The relative standard deviation of the maximum power was 4.76 %. The maximum power point tracking (MPPT), steady-state (or stabilized) power output (SPO) and dynamic I-V measurements were also performed as the steady-state measurements of the maximum power. An excellent consistency was found to exist between the maximum powers obtained by the MPPT, SPO and dynamic I-V methods. The relative standard deviation of Pmax determined by the MPPT method at KISTEC and AIST was 1.25 %.

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