Solar cells: past, present, future

This paper gives an up to date perspective of PV technology and materials. The most important material has been and still is silicon. It dominates the present world market, particularly in its crystalline form but amorphous silicon is also of importance. Crystalline silicon solar cells are still heavily dependent on the materials base of the semiconductor industry. This material still has a large potential for cost reduction in its conventional form and even more so in the crystalline thin film version. Great hope rests with the thin film materials which require only small amounts of material. A great number of new concepts and materials are still in the research stage. Some of them may lead to much higher efficiency and lower cost in the coming decades. A function was identified which can be fitted to the past development of the best laboratory efficiencies. By fitting this function to the data points the future development of efficiency can be estimated for each technology.