Conventional crystalline-silicon pn solar cells can be simply understood in principle. Complications arise from the emitter doping profile. A one-dimensional multi-region method appears as a natural tool to solve the continuity equation for minority carriers in emitter and base, joining the junction on both sides. The generation of photocarriers may be partitioned in space, and the photocurrent pieces summed up. The regional method operates in this way. The method extends analytical analysis, and can be further extended to organize full one-dimensional device modeling.