Relations between morphology and electro-optical properties of MDMO-PPV: PCBM bulk heterojunction organic solar cells

Abstract

Introduction: The present use of today’s main fuel sources will inevitably lead to shortage and eventually to a running out of these energy supplies. Together with diminishing supplies, the energy demand grows every day. By the year 2050, worldwide energy demand is projected by the World Energy Council to be at least double its present level. But demand-supply is not a stand-alone problem. Toxic waste, inseparable connected to present energy production by means of coal, oil and uranium can have a dramatic impact on climate and environment. These present-day and future problems have led to a search for renewable, environment friendly energy resources: solar, water and wind energy, which can all be reduced to the energy of the sun. Every year, the sun beams down several 1000 times the world’s annual energy demand on our planet. Photovoltaic cells are used to directly convert this less useful energy into very useful electrical power. This harvesting of solar energy is one of the most promising candidates to provide in future energy demands. Prices for photovoltaic modules have been dropping down to $5 per Watt peak. This is cheap enough to accommodate some niche markets, but to capture much larger markets, cost must be dropped further. At the moment, they are not yet cheap enough for solar energy to compete with classic energy prices in other than specialized applications without government aid. Waiting for present energy prices to surpass those of solar power is not an option. Therefore, huge efforts are being made to lower prices for solar energy conversion using several approaches: use of low-cost, high-yield processes, mass production, new technologies: making of more efficient cells (reducing area and increasing efficiency per square meter) and increasing module lifetime, use of cheaper materials....