The thermal and electrical performance of the photovoltaic-thermal (PVT) system still needs to be improved although the system has been widely applied. In this study, the performance of a multilayer-structured PVT system with phase change materials (PCMs) is investigated experimentally and numerically. The novel design of layout scheme of heat exchanger is introduced, and a detailed mathematical model of the heat transfer process and operational efficiency of the PVT system is developed. Subsequently, the temperature variation of the PVT system is simulated and verified by measurements based on an outdoor experimental system. According to the measurements and calculation by using a homemade MATLAB code, the characteristic temperature and efficiencies of the PVT system are predicted. The results show that the forecasted temperature variation of the PVT system agrees well with the practical system. The average electrical efficiency of the PVT system can increase by around 1% by using the heat exchanger with PCMs. Meanwhile, the thermal efficiency is raised due to the prolonged operation time. The composite PCM with 15% expanded graphite may enhance the comprehensive efficiency by 25.2%. Moreover, the database of the performance of practical PVT systems in East Shanghai is supplemented with measured and evaluated values. (C) 2020 Elsevier Ltd. All rights reserved.