Sorry if this has been asked and answered. I did a search but came up empty.
I use this not very fancy, but quick method to achieve that. Because I do not only want it on my second screen but also maximized I don't have to be too precise on the coordinates. Any X-coordinate above 2000 is usually on the second screen for all my dev machines: (This example uses chromedriver but works with any IWebDriver)
chrome = new ChromeDriver();
chrome.Manage().Window.Position = new System.Drawing.Point(2000, 1); // To 2nd monitor.
chrome.Manage().Window.Maximize();