Dust deposition causes a significant loss of performance of a high-concentration photovoltaic thermal (HCPV/T) system. In this paper, the influence of dust deposition on the output performance of a gallium arsenide cell HCPV/T with a Fresnel lens was investigated using a dust deposition test. The changes in the thermoelectric and exergy performance of the system were analyzed at different dust densities. The influence of the dust particle size on the relative overall efficiency was determined. The results showed that the thermal efficiency and electrical efficiency decreased by 2.65% and 1.29%, respectively, for a 1 g/m(2) increase in the dust density. At the same dust density, the relative overall efficiency was lower for the smaller dust particle size. Model fitting and calculations indicated that the rate of decline in power output reached the maximum at a dust density of 9.84 g/m(2). The results provide references for similar experiments. (c) 2020 Published by Elsevier Ltd.