Polymer solar cells are considered as very promising condidates for development of photovoltaics of the future. They are cheap and easy to fabricate, however, up to now, they posses fundamental drawback: low effectiveness. In the most popular BHJ (bulk heterofunction) architecture the actual long-standing top efficiency is 12%. One ask the question how fundamental this limitation is, as certain considerations suggest that it should be two times higher. We describe our simulations on possible influence of so called 'geometric factor' on total efficiency, sketch possibel influence of some other factors, and argue that limitations of BHJ architecture are inevitable. We speculate also on perspectives of development of organic solar cells using other ideas.