The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage. NEW YORK ( Trefis) -- Suntech Power ( STP), the world's largest manufacturer of PV modules, may see more bad days ahead as the fall in demand for its product becomes more acute over the next couple of quarters. The latest indication of a larger-than-anticipated fall in module demand came after an ominous decline in the spot price of polysilicon, the primary raw material in the manufacture of multi-crystalline PV modules. We recently revised our estimates for SunTech, First Solar ( FSLR) and SunPower ( SPWRA), all of the solar firms that fall under our coverage. Click here for our full analysis of SunTech Power. The spot price for polysilicon fell 5.8% in the week ending Oct. 10, the largest drop in prices since June of this year. The price of multi crystalline solar cells also declined by 4.1% in the same period to 70 cents. The latest decline in pricing reflects the effects of the European debt crisis on PV installations in European markets such as Germany and Italy, which accounted for 84% of the solar module industry in 2010, among other factors. In September, Goldman Sachs cut its forecasts for panel demand in the second half of 2011 by 18%. Polysilicon manufacturers also have to contend with a number of Chinese plants coming into the market and Qatar announcing a $1 billion polysilicon manufacturing plant expected to come online in 2013. Solar companies are trying to offset reduced demand from European nations by diversifying their customer base and targeting emerging markets and the U.S. In the long term, reduced costs spread across the PV value chain are expected to make the end cost of generating solar electricity comparable to the retail price of purchasing electricity in many markets resulting in lesser dependence of the industry on government subsidies. Polysilion prices have fallen by 45% since they peaked in March this year. The falling spot price of polysilicon may not result in an immediate decline in the costs incurred by module manufacturers as almost 90% of the market falls under long-term contracts. Spot prices account for a small fraction of the overall sales of polysilicon and the recent bankruptcy of some solar firms has resulted in more material being released into the spot market.